THE DC-UPS OF THE SERIES C-TEC INCLUDES ULTRA-CAPACITORS AS ENERGY STORAGE INSIDE THE HOUSING. THIS CAPACITOR IS CHARGED WITH THE SYSTEM VOLTAGE (UE) DURING NORMAL OPERATION. THE CONNECTED LOADS ARE SUPPLIED AS WELL FROM THE SYSTEM VOLTAGE. IN CASE OF AN INTERRUPTION OF THE SYSTEM VOLTAGE THE ENERGY OF THE ULTRA-CAPACITORS IS RELEASED IN A REGULATED WAY. WITH A DC/DC CONVERTER; THE LOAD IS SUPPLIED BY THE CAPACITOR UNTIL IT IS DISCHARGED. THE BACK-UP TIME DEPENDS ON THE STATE OF CHARGE OF THE CAPACITOR AND ON THE DISCHARGE CURRENT.